$25. 002009 ieee 52 ieee

Challenges with Large Penetration 

of Intermittent Resources

Wind has been the fastest growing segment of the renew-

able industry. Solar generation is lagging behind, but new 

advances in technology show great promise for solar genera-

tion, which could catch up to and even overtake wind gen-

eration. New wind or solar power generation facilities can be 

installed, interconnected, and commissioned in a relatively 

short time frame, provided that the grid can handle the new 

capacity. The economics of these resources are fast improv-

ing, reaching a close parity with fossil generation. Figure 1 

shows a comparison of capital costs for new generation us-

ing various technologies.

Over the past two decades, wind technology has improved 

signifi cantly with turbines as large as 6 MW and costs below 

$2 million per megawatt of installed capacity; large wind 

farms with several hundred megawatt capacities are being 

deployed over several months. 

Within the next few years, new solar photovoltaic (PV) 

manufacturing facilities in many regions of the country 

promise to add enough capacity to produce thousands of 

megawatts of solar cells and modules per year. New tech-

nologies, such as depositing solar modules onto a fl exible 

plastic substrate or using solar “inks” (e.g., copper indium 

gallium selenide) and a “printing” process to produce thin 

fi lm solar panels, are poised to drastically reduce the cost of 

solar power plants to less than $1 per watt.

Solar power plants can be built where they are most need-

ed in the grid because siting PV arrays is usually much easier 

than siting a conventional power plant. Furthermore, unlike 

conventional power plants, modular PV plants can be ex-

panded incrementally as demand increases. It is anticipated 

that municipal solar power plants with few megawatt capac-

ity built close to load centers will become common during 

the next decade. 

However, these intermittent renewable resources pose 

many challenges for the grid and grid operators: